Al-Qaeda leader Ayman al-Zawahiri
Al-Qaeda leader Ayman al-ZawahiriAFP file

Ayman al-Zawahiri, Osama bin Laden's replacement as the Head of Al Qaeda, has called for more attacks similar to the bombing of the Boston Marathon that he said would 'bleed America' into expending crippling security costs.

The incitement to commit further terrorist attacks came in the form of an audio message marking the 12th anniversary of the 11th September 2001 attacks.

"We must bleed America economically by provoking it, so that it continues its massive expenditures on security. America's weak spot is its economy, which began to totter from the drain of its military and security expenditure," Zawahiri said.

"Just as we defeated it in a war of nerves in Somalia, Yemen, Iraq and Afghanistan, we must afflict it with a similar war in its own home." Zawahiri said. Adding "These dispersed strikes can be carried out by one brother, or a small number of brothers."

The message also urged an economic boycott on the Unites States leading analysts to suggest the terrorist organization no longer had the capability to carry out centrally organized attacks.

A BBC report said: "Most analysts believe that the Al-Qaeda core in Pakistan has been severely damaged and this message appears to be an acknowledgement of that reality." The report added: "The message may be seen as a sign of diminishing ambitions and a more realistic assessment of what al-Qaeda's central organisation can achieve."

Zawahiri, who jointly created Al Qaeda with Osama Bin Laden, took over the sole running of the terrorist network in 2011 killing of Bin laden by US special forces in Pakistan.  An Egyptian born physician has spent over 35 years involved in terrorist  plots first arrested in 1981 in connection with an assassination attempt on then Egyptian President Anwar Sadat .

In his recording, Zawahiri also turned to the Middle East. After claiming the ousting of the Muslim Brotherhood from rule in Egypt was an American plot, he took aim at deposed President Mohammed Morsi, saying he did not govern according to Islamic law and had committed to abide by security agreements with the US and Israel.